Nitrox - 1.40 or 1.60 PO2?

[OH-JJ]

Papa can say all he likes. after talking with many Tec divers, and with talking to Commercial divers, that have held there friends in there arms while Ox-Tox'ing. I know that I will never exceed 1.6 at rest and 1.4 while working. you can push the limits if you are in a full face mask and with a buddy to pull you up while toxing, but if you tox with a normal reg in your mouth onl, you will drown... You have to descide if you are good with that.

Personally I would rateher Tox first than drown, but I would prefer to live.

 

[texdiveguy]

Another good source of basic information related to the OP's question............

DAN Divers Alert Network : OXTOX: If You Dive Nitrox You Should Know About OXTOX

Follow prevailing prescribed guide lines for PPO2 when diving. This is an area that is important for all divers to have a basic working knowledge of.

I do not recommend for any diver within the recreational group to exceed a PPO2 of 1.4 without the proper training and skills in dealing with decompression diving, and then to follow proper taught protocols. Pushing the envelope as a few divers might do can be costly.

 

[TSandM]

The big problem with oxygen toxicity is that susceptibility varies wildly between individuals, and in the SAME individual from day to day. The second problem is that very few people survive a full-blown oxygen toxicity event. It is very difficult to set guidelines for an event where the threshold of onset is extremely hard to define, but where the desired frequency of the outcome is zero.

There have been only a tiny number of fairly clear-cut oxygen toxicity events recorded at 1.4. To my knowledge, there have been none at 1.2. Since CO2 retention potentiates oxygen toxicity, it may be wise to use a lower ppO2 at deeper depths or when working significantly (eg. swimming against current or flow). Some technical divers use 1.4 for working ppO2 and 1.6 for deco, but many of them dive with buddies who have been trained to recognize and perform rapid rescue in the event of a tox. In addition, the 1.6 is used during a period of the dive where the diver is not moving or working.

I use a max of 1.4, contingency of 1.6, but work very hard to avoid any contingency that would require me to go to the higher limit.

 

[Papa_Bear]

Papa can say all he likes. after talking with many Tec divers, and with talking to Commercial divers, that have held there friends in there arms while Ox-Tox'ing. I know that I will never exceed 1.6 at rest and 1.4 while working. you can push the limits if you are in a full face mask and with a buddy to pull you up while toxing, but if you tox with a normal reg in your mouth onl, you will drown... You have to descide if you are good with that.

Personally I would rateher Tox first than drown, but I would prefer to live.

Did you read the link? We are talking rec diving here, 99% of all diving is not within the curve that will get you in trouble with a single tank of 36% past 100ft for 40 min.! If you read what I posted 1.6 is my hard bottom, but do you know what it takes to get there? Maybe you need a better computer? But this isn't Voodoo, Howdoo, and of that scary stuff that happens in the old Carib! It is manageable and no reported hits have been reported 1.6 or below, only above at depth and time beyond 99% of the readers here! My point is be knowledgeable and informed and make it a personal choice! You have a bigger chance of a bubble on Air than a Tox hit at 1.6 a much bigger one! Its all about perspective!

 

[OH-JJ]

Did you read the link? We are talking rec diving here, 99% of all diving is not within the curve that will get you in trouble with a single tank of 36% past 100ft for 40 min.! If you read what I posted 1.6 is my hard bottom, but do you know what it takes to get there? Maybe you need a better computer? But this isn't Voodoo, Howdoo, and of that scary stuff that happens in the old Carib! It is manageable and no reported hits have been reported 1.6 or below, only above at depth and time beyond 99% of the readers here! My point is be knowledgeable and informed and make it a personal choice! You have a bigger chance of a bubble on Air than a Tox hit at 1.6 a much bigger one! Its all about perspective!

I have a VR-3 on my arm.
a 40 of 50% O2 on my left side.
My best friend and most trusted dive buddy, was a Commercial diver with dives over 500ft, and over 4000 logged dives in his commercial log books which stopped 13 years ago.

I Know the risks...
I know what they teach...
I know my Real limits...
But I know what I run normally...

I know I will NEVER run 1.6 PO2 for a bottom gas while doing physical exertion.

I know I will maybe, (in extreme measures,) breath my deco gas if I loose back gas at depth, but I will NEVER recommend it, and I will also be heading up at that time.

Yes you want to know the truth, my best way to die under water is to Ox-Tox. I really do not want to die though.

 

[DandyDon]

Did you read the link? We are talking rec diving here, 99% of all diving is not within the curve that will get you in trouble with a single tank of 36% past 100ft for 40 min.! If you read what I posted 1.6 is my hard bottom, but do you know what it takes to get there? Maybe you need a better computer? But this isn't Voodoo, Howdoo, and of that scary stuff that happens in the old Carib! It is manageable and no reported hits have been reported 1.6 or below, only above at depth and time beyond 99% of the readers here! My point is be knowledgeable and informed and make it a personal choice! You have a bigger chance of a bubble on Air than a Tox hit at 1.6 a much bigger one! Its all about perspective!

PB may seem a bit rough in the way he expresses himself at times, and many could say the same about me at times, but anyway - I tend to agree with him here. I drive slower that most to conserve gas but feel comfortable driving 70-80 mph without a helmet, and set both my computers on 1.6 max - but avoid it, which is generally easy to do. If I see 1.42 or more, I consider my actions but I don't freak.

When I first got my Nx card, I did a wreck dive with a boat-pic air-diving buddy and told him that my 1.4 MOD was whatever which happen to be only a few feet below the deck of the ship, and that was part of our dive plan. Dive plans do not include "turn left at the third coral head" type details in recreational diving of course, and actual details will vary somewhat even while diving the plan - but he dropped down to the sand at one point. I was horrified and not about to follow him down even if he got into trouble - but I was wrong. 1.4 suggested, 1.6 contingent if not working hard, and I've oops beyond that once at idle exertion which I plan to never allow to happen again, as far as plans go.

 

[OH-JJ]

PB may seem a bit rough in the way he expresses himself at times, and many could say the same about me at times, but anyway - I tend to agree with him here. I drive slower that most to conserve gas but feel comfortable driving 70-80 mph without a helmet, and set both my computers on 1.6 max - but avoid it, which is generally easy to do. If I see 1.42 or more, I consider my actions but I don't freak.

When I first got my Nx card, I did a wreck dive with a boat-pic air-diving buddy and told him that my 1.4 MOD was whatever which happen to be only a few feet below the deck of the ship, and that was part of our dive plan. Dive plans do not include "turn left at the third coral head" type details in recreational diving of course, and actual details will vary somewhat even while diving the plan - but he dropped down to the sand at one point. I was horrified and not about to follow him down even if he got into trouble - but I was wrong. 1.4 suggested, 1.6 contingent if not working hard, and I've oops beyond that once at idle exertion which I plan to never allow to happen again, as far as plans go.

Again...
I know the Risks and I know what I will do in the situations, as needed.

but I also know what I will recommend.

it is that same as saying that If you don't know what 60 at 60 is, then you should not be pushing it.

yes you can push your PO2 for a few minutes, depending on your level of activity, but unless you know that limit, or what it involves, why risk pushing it?

In real Life I do push MY limits, but I know what they are and the risks involved.

This is not in real life.

 

[Gene_Hobbs]

Read this and you will understand my point of view! OXYGEN EXPOSURE MANAGEMENT

That was a good article when it came out but even Dick (author from above link) has gone so far as to suggest even a 1.2 might be a better solution given the risk. His presentation from the DAN Tech Conference is excellent and free so nobody has an excuse for not checking it out.

Richard Vann, PhD, 2008 DAN Technical Diving Conference

 

[The Kraken]

I'm not going to tell anyone how to dive or what limits to use, but . . .

What once was set forth as a suggestion based upon an increase in oxygen toxicity, for some reason that escapes me, has now become some sort of a scubadiving quasi-law.

When ox-tox studies were done, it was shown that the possibility of incurring oxygen toxicity increased as one exceeded 1.6 PPO2.

So, agencies suggest that to stay a little safer, plan the dives based upon a PPO2 of 1.4.

So now it seems that some think 1.4 is the barrier so they're utilizing an even lesser PPO2.

I suggest you do some in depth reading of the subject matter and come to your own conclusion.

the K

 

[Gene_Hobbs]

I suggest you do some in depth reading of the subject matter and come to your own conclusion.

Best advice in this thread yet.

A good history of all this covered in the DAN Nitrox Workshop Proceedings.

Lang, MA (ed) 2001. DAN Nitrox Workshop Proceedings. Divers Alert Network, Durham, N.C., 197p. RRR ID: 4855

and of course more reading.